U.S. patent number 11,052,006 [Application Number 15/401,552] was granted by the patent office on 2021-07-06 for aspirator or pressurizer.
This patent grant is currently assigned to MURATA MANUFACTURING CO., LTD.. The grantee listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Nobuhira Tanaka.
United States Patent |
11,052,006 |
Tanaka |
July 6, 2021 |
Aspirator or pressurizer
Abstract
An aspirator includes a pump, a detecting unit, and a control
unit. The pump is driven by a piezoelectric element and has a
suction portion and a discharge portion. The detecting unit
includes a current detector and a regulator, and detects a closed
state of the suction portion. The control unit includes the
regulator and a voltage controller, and regulates an output voltage
for the piezoelectric element in accordance with the closed state
of the suction portion detected by the detecting unit.
Inventors: |
Tanaka; Nobuhira (Kyoto,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Kyoto |
N/A |
JP |
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Assignee: |
MURATA MANUFACTURING CO., LTD.
(Kyoto, JP)
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Family
ID: |
1000005663283 |
Appl.
No.: |
15/401,552 |
Filed: |
January 9, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170112697 A1 |
Apr 27, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2015/069851 |
Jul 10, 2015 |
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Foreign Application Priority Data
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Jul 11, 2014 [JP] |
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JP2014-143125 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61G
7/057 (20130101); A61M 1/80 (20210501); A61M
1/00 (20130101); A61M 1/84 (20210501); A61M
2205/3334 (20130101); A61M 2205/583 (20130101); A61M
2210/0618 (20130101) |
Current International
Class: |
A61G
7/057 (20060101); A61M 1/00 (20060101) |
Field of
Search: |
;417/19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2000060962 |
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Feb 2000 |
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JP |
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2001218831 |
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Aug 2001 |
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JP |
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2007117273 |
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May 2007 |
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JP |
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2010527636 |
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Aug 2010 |
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JP |
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2013050034 |
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Mar 2013 |
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JP |
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2013532246 |
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Aug 2013 |
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JP |
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Other References
Extended European Search Report for 15 81 8979 dated Feb. 5, 2018.
cited by applicant .
Written Opinion of WO2016/006677 dated Sep. 1, 2015. cited by
applicant .
International search report of WO2016/006677 dated Sep. 1, 2015.
cited by applicant.
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Primary Examiner: Tremarche; Connor J
Attorney, Agent or Firm: Pearne & Gordon LLP
Parent Case Text
This application is a continuation of International Application no.
PCT/JP2015/069851 filed on Jul. 10, 2015 which claims priority from
Japanese patent application no. JP 2014-143125 filed on Jul. 11,
2014. The contents of these applications are incorporated herein by
reference in their entireties.
Claims
The invention claimed is:
1. An aspirator or pressurizer comprising: a pump driven by a
piezoelectric element and having an inlet and an outlet; and a
circuit configured to: detect whether the inlet or the outlet is in
a closed state; and regulate a voltage output to the piezoelectric
element based on detection of the closed state of the inlet or the
outlet, wherein the circuit is further configured to detect the
closed state in part by detecting an impedance of the piezoelectric
element, and wherein the circuit detects that the inlet or the
outlet is in the closed state when a measured amplitude of current
flowing through the piezoelectric element is greater than a
threshold amplitude.
2. The aspirator or pressurizer according to claim 1, wherein the
circuit is configured to lower the voltage output to the
piezoelectric element if the circuit detects that the inlet or the
outlet is in the closed state.
3. The aspirator or pressurizer according to claim 1, wherein the
circuit is configured to raise the voltage output to the
piezoelectric element if the circuit detects that the inlet or the
outlet is in the closed state.
4. The aspirator or pressurizer according to claim 1, further
comprising an indicator configured to display an indication of the
closed state of the inlet or the outlet.
5. The aspirator or pressurizer according to claim 1, wherein an
object to be suctioned by the aspirator or pressurizer is nasal
mucus.
6. An aspirator or pressurizer comprising: a pump driven by a
piezoelectric element and having an inlet and an outlet; and a
circuit configured to: detect whether the inlet or the outlet is in
a closed state; and regulate a voltage output to the piezoelectric
element based on detection of the closed state of the inlet or the
outlet, wherein the circuit is further configured to detect the
closed state in part by detecting an impedance of the piezoelectric
element, wherein the circuit is configured to detect the closed
state in part by using a frequency at which a magnitude of the
impedance of the piezoelectric element is minimized.
7. An aspirator or pressurizer comprising: a pump having an inlet
and an outlet; and a circuit configured to: detect whether the
inlet or the outlet is in a closed state or an open state; raise a
drive voltage of the pump when the circuit detects that the inlet
or the outlet is in the closed state; and lower the drive voltage
of the pump when the circuit detects that the inlet or the outlet
is in the open state, wherein the circuit detects that the inlet or
the outlet is in the closed state when a measured amplitude of
current flowing through a piezoelectric element is greater than a
threshold amplitude.
8. The aspirator or pressurizer according to claim 7, wherein the
piezoelectric element is driven by the drive voltage.
9. The aspirator or pressurizer according to claim 7, wherein the
circuit is further configured to detect whether a flow passage
communicating with the suction portion or the discharge portion is
in a closed state.
Description
BACKGROUND
Technical Field
The present disclosure relates to an aspirator or pressurizer
including a pump.
Examples of conventional aspirators include a nasal mucus aspirator
described in Patent Document 1. The nasal mucus aspirator includes
a vacuum generator, a nasal mucus storage cylinder, a suction tube,
and an actuator. The vacuum generator and the nasal mucus storage
cylinder are coupled to each other by a tube. The nasal mucus
storage cylinder is coupled to the suction tube for suctioning
nasal mucus. The actuator is configured to start and stop
suctioning of the nasal mucus. In this nasal mucus aspirator, when
the suction tube is inserted into a nasal cavity and a button of
the actuator is pressed, the nasal mucus is suctioned from the
suction tube by a vacuum generated by the vacuum generator, and
then is stored in the nasal mucus storage cylinder. When the button
of the actuator is released, the vacuum is released and the
suctioning is stopped.
Examples of conventional pressurizers include one that is used in
an anti-bedsore bed. In a conventional anti-bedsore bed, air cells
inflated by being pressurized by a pressurizer raise one side of
the user's body. This allows the user to turn over, thereby
preventing a user's bedsore.
Patent Document 1: Japanese Unexamined Patent Application
Publication No. 2001-218831
BRIEF SUMMARY
In the nasal mucus aspirator described in Patent Document 1, since
suctioning continues at constant suction pressure, the suction
pressure of the nasal mucus aspirator needs to be set high to
ensure reliable suctioning of the nasal mucus. However, this
increases the power consumption of the nasal mucus aspirator during
operation. Additionally, if the suction tube does not successfully
hit the nasal mucus, a large amount of air may be suctioned all at
once from the nasal cavity, and this may negatively affect the
human body. On the other hand, if the suction pressure of the nasal
mucus aspirator is set low to avoid the problems described above,
nasal mucus of high viscosity may not be able to be removed. Since
the conventional anti-bedsore bed is unable to detect the turning
of the user, the pressurizer applies excessive pressure to the air
cells for a long period of time. This results in increased power
consumption and noise of the pressurizer.
The present disclosure provides an aspirator or pressurizer capable
of applying appropriate pressure in accordance with the
situation.
An aspirator or pressurizer according to the present disclosure
includes a pump, a detecting unit, and a control unit. The pump is
driven by a piezoelectric element and has a suction portion and a
discharge portion. The detecting unit is configured to detect a
closed state of the suction portion or the discharge portion. The
control unit is configured to regulate an output voltage for the
piezoelectric element in accordance with the closed state of the
suction portion or the discharge portion detected by the detecting
unit.
With this configuration, the output voltage for the piezoelectric
element is automatically regulated in accordance with the closed
state of the suction portion. For example, when it is difficult to
suction nasal mucus, the amplitude of the output voltage is
increased and the nasal mucus is suctioned by high suction
pressure. When it is easy to suction nasal mucus, the amplitude of
the output voltage is set to a medium level and the nasal mucus is
suctioned by low suction pressure. When suctioning of nasal mucus
is completed or there is no nasal mucus, the amplitude of the
output voltage is reduced. Since the aspirator can thus be operated
by a minimum voltage, its power consumption during operation can be
reduced.
The amplitude of the output voltage is increased only when it is
difficult to suction the nasal mucus. In other words, the amplitude
of the output voltage is reduced when suctioning of the nasal mucus
is completed or there is no nasal mucus. Thus, since it is unlikely
that a large amount of air is suctioned out of the nasal cavity, a
negative impact on the human body can be reduced.
When the pressurizer is used in an anti-bedsore bed, the closed
state of the discharge portion of the pump varies depending on
whether the user has turned over. Therefore, with the configuration
of the present disclosure, the output voltage for the piezoelectric
element is automatically regulated depending on whether the user
has turned over. Thus, by simply driving the pump for a minimum
period of time at a minimum output, it is possible to allow the
user to turn over and prevent a user's bedsore. That is, the power
consumption and noise of the pressurizer used in the anti-bedsore
bed can be reduced.
In the aspirator or pressurizer according to the present
disclosure, the detecting unit may detect a pressure difference
between the suction portion and the discharge portion. The pressure
difference between the suction portion and the discharge portion
varies depending on whether the suction portion or the discharge
portion is closed. Therefore, with this configuration, the closed
state of the suction portion or the discharge portion can be
detected by detecting the pressure difference between the suction
portion and the discharge portion. Also, by varying the amplitude
of the output voltage in a stepwise manner and detecting the
suction pressure accordingly, the level of difficulty in suctioning
the nasal mucus can be determined.
In the aspirator or pressurizer according to the present
disclosure, the detecting unit may detect a rate of flow from the
suction portion to the discharge portion. The rate of flow varies
depending on whether the suction portion or the discharge portion
is closed. Therefore, with this configuration, in the same manner
as above, the closed state of the suction portion or the discharge
portion can be detected by detecting the rate of flow.
In the aspirator or pressurizer according to the present
disclosure, the detection by the detecting unit can involve using
an impedance of the piezoelectric element. An amount related to the
impedance of the piezoelectric element, such as the magnitude or
phase of the impedance of the piezoelectric element or a frequency
at which the magnitude of the impedance of the piezoelectric
element is minimized, varies depending on whether the suction
portion or the discharge portion is closed. Therefore, with this
configuration, the closed state of the suction portion or the
discharge portion can be detected by using the impedance of the
piezoelectric element.
In the aspirator or pressurizer according to the present
disclosure, the detection by the detecting unit may involve using a
magnitude of the impedance of the piezoelectric element at a drive
frequency of the pump. The magnitude of the impedance of the
piezoelectric element is the amplitude ratio between the current
flowing through the piezoelectric element and the output voltage
for the piezoelectric element. Therefore, with this configuration,
the closed state of the suction portion or the discharge portion
can be detected by measuring the current flowing through the
piezoelectric element. Also, in the case of measuring the current,
the number of components of a circuit implementing the detecting
unit can be reduced. It is thus possible to reduce the size of the
circuit implementing the detecting unit.
In the aspirator or pressurizer according to the present
disclosure, the detection by the detecting unit may involve using a
phase of the impedance of the piezoelectric element at a drive
frequency of the pump. The phase of the impedance of the
piezoelectric element is a phase difference between the current
flowing through the piezoelectric element and the output voltage
for the piezoelectric element. Therefore, with this configuration,
the closed state of the suction portion or the discharge portion
can be detected by measuring the phase difference between the
current flowing through the piezoelectric element and the output
voltage for the piezoelectric element. Also, since the measurement
of the phase difference is less affected by changes in temperature,
it is possible to accurately regulate the suction pressure or
pressurizing force.
In the aspirator or pressurizer according to the present
disclosure, the detection by the detecting unit may involve using a
frequency at which a magnitude of the impedance of the
piezoelectric element is minimized. The frequency at which the
magnitude of the impedance of the piezoelectric element is
minimized is a resonant frequency of the piezoelectric element.
Therefore, with this configuration, the closed state of the suction
portion or the discharge portion can be detected by calculating the
resonant frequency of the piezoelectric element. Also, by adjusting
the drive frequency of the pump to the resonant frequency, it is
possible to increase the vibration of the piezoelectric element and
achieve high suction pressure or pressurizing force without
necessarily varying the amplitude of the output voltage.
The aspirator or pressurizer according to the present disclosure
may further include an indicator configured to display the closed
state of the suction portion or the discharge portion detected by
the detecting unit. With this configuration, the closed state of
the suction portion or the discharge portion can be displayed by
the indicator.
In the aspirator according to the present disclosure, an object to
be suctioned may be nasal mucus. With this configuration, nasal
mucus can be suctioned.
According to the present disclosure, an aspirator or pressurizer
capable of applying appropriate pressure in accordance with the
situation can be obtained.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic cross-sectional view of an aspirator
according to a first embodiment.
FIG. 2 is a cross-sectional view of a piezoelectric pump according
to the first embodiment.
FIGS. 3A-3C are schematic diagrams illustrating different vibration
modes of the piezoelectric pump according to the first
embodiment.
FIG. 4 is a block diagram of a circuit unit according to the first
embodiment.
FIG. 5 is a graph showing the amplitude of current flowing through
a piezoelectric element 22 with respect to the amplitude of drive
voltage applied to the piezoelectric element 22.
FIG. 6 is a flowchart illustrating an operation of the circuit unit
according to the first embodiment.
FIG. 7A is a conceptual diagram illustrating how the amplitude of
drive voltage changes with time in suctioning of low-viscosity
nasal mucus, FIG. 7B is a conceptual diagram illustrating how the
amplitude of drive voltage changes with time in suctioning of
medium-viscosity nasal mucus, and FIG. 7C is a conceptual diagram
illustrating how the amplitude of drive voltage changes with time
in suctioning of high-viscosity nasal mucus.
FIG. 8A is a conceptual diagram illustrating how the amplitude of
drive voltage, the suction pressure, and the flow rate change with
time in an aspirator having a conventional configuration, and FIG.
8B is a conceptual diagram illustrating how the amplitude of drive
voltage, the suction pressure, and the flow rate change with time
in the aspirator according to the first embodiment.
FIG. 9 is a block diagram of a circuit unit according to a second
embodiment.
FIG. 10 is a flowchart illustrating an operation of the circuit
unit according to the second embodiment.
FIG. 11 is a block diagram of a circuit unit according to a third
embodiment.
FIG. 12 is a flowchart illustrating an operation of the circuit
unit according to the third embodiment.
FIG. 13 is a schematic cross-sectional view for explaining a
negative pressure wound therapy according to a fourth
embodiment.
FIG. 14 is a flowchart illustrating an operation of an aspirator
according to the fourth embodiment.
FIGS. 15A and 15B provide external perspective views and an
exploded perspective view of an anti-bedsore bed according to a
fifth embodiment.
FIGS. 16A and 16B provide side views of the anti-bedsore bed
according to the fifth embodiment.
FIG. 17 is a flowchart illustrating an operation of a drive circuit
unit corresponding to an air cell 73A.
DETAILED DESCRIPTION
First Embodiment
An aspirator 10 according to a first embodiment of the present
disclosure will be described. The aspirator 10 is used to suction
nasal mucus. FIG. 1 is a schematic cross-sectional view of the
aspirator 10. The aspirator 10 includes a nozzle 11, a separator
12, and a piezoelectric drive unit 13 arranged in this order from
front to rear. The aspirator 10 has a flow passage 14 that connects
the front end of the nozzle 11 to the rear end of the piezoelectric
drive unit 13. The separator 12 includes a storage unit 15 that
branches off the flow passage 14. The piezoelectric drive unit 13
includes a piezoelectric pump 21 (see FIG. 2) and a circuit unit 31
(see FIG. 4) for driving the piezoelectric pump 21. The
piezoelectric pump 21 corresponds to a pump of the present
disclosure. The aspirator 10 includes an indicator (not shown)
configured to display the state of the front end of the nozzle
11.
In the aspirator 10, the front end of the nozzle 11 is inserted
into the nasal cavity for suctioning nasal mucus. When the
piezoelectric drive unit 13 is driven, a flow of air from the front
end of the nozzle 11 to the rear end of the piezoelectric drive
unit 13 is generated in the flow passage 14. Nasal mucus in the
nasal cavity is suctioned from the front end of the nozzle 11
together with air, separated in the separator 12, and stored in the
storage unit 15.
FIG. 2 is a cross-sectional view of the piezoelectric pump 21. The
piezoelectric pump 21 includes a piezoelectric element 22 and a
structure 23. The structure 23 has a generally disk-like outer
shape and is thin in the thickness direction. A discharge port 26
is open near the center of the top surface of the structure 23. A
suction port 27 is open near the edge of the bottom surface of the
structure 23. The piezoelectric pump 21 is positioned with the
suction port 27 facing the nozzle 11. The discharge port 26
corresponds to a discharge portion of the present disclosure. The
suction port 27 corresponds to a suction portion of the present
disclosure.
The structure 23 is internally provided with a flow passage 24 and
a pump chamber 25. The flow passage 24 communicates with the
discharge port 26 on the top surface of the structure 23. In the
structure 23, the flow passage 24 extends from around the center
toward the outer edge of the structure 23, and communicates with
the suction port 27 on the bottom surface of the structure 23. The
pump chamber 25 is a thin circular cylindrical space provided on
the bottom side of the portion where the discharge port 26 and the
flow passage 24 communicate with each other. The pump chamber 25 is
open to the portion where the discharge port 26 and the flow
passage 24 communicate with each other.
The inner bottom surface of the pump chamber 25 in the structure 23
is configured as a diaphragm (vibrating plate) 28 capable of
bending and vibrating. The diaphragm 28 has a disk-like shape. The
top surface of the diaphragm 28 faces the pump chamber 25, and the
piezoelectric element 22 is affixed to the bottom surface of the
diaphragm 28. The top surface of the diaphragm 28 is disposed
opposite the discharge port 26, with the pump chamber 25 interposed
therebetween. The piezoelectric element 22 is a disk-shaped member
which is thin in the thickness direction. The piezoelectric element
22 has piezoelectricity which allows the piezoelectric element 22
to expand and contract in the in-plane direction of the principal
surface thereof by being subjected to an alternating voltage.
FIGS. 3A-3C are schematic diagrams illustrating different vibration
modes of the piezoelectric pump 21. The piezoelectric element 22
and the diaphragm 28 are affixed to each other to form a unimorph
structure, which is displaced in the thickness direction by driving
the piezoelectric element 22. Specifically, when the piezoelectric
element 22 tries to expand from a resting state, such as that
illustrated in FIG. 3A, the diaphragm 28 bulges toward the
piezoelectric element 22 (i.e., toward the bottom side) as
illustrated in FIG. 3B to increase the volume of the pump chamber
25. Thus, a negative pressure is generated in the pump chamber 25
and transmitted to the flow passage 24 communicating with the pump
chamber 25, and a fluid in the flow passage 24 is suctioned into
the pump chamber 25.
When the piezoelectric element 22 tries to contract, the diaphragm
28 bulges toward the pump chamber 25 (i.e., toward the top side) as
illustrated in FIG. 3C to reduce the volume of the pump chamber 25.
Since the pump chamber 25 and the discharge port 26 are disposed
opposite each other with the flow passage 24 interposed
therebetween, a fluid in the pump chamber 25 is discharged through
the discharge port 26 to the outside. At the same time, a fluid in
the flow passage 24 is drawn into the flow of the fluid from the
pump chamber 25 and discharged through the discharge port 26.
As described above, in the piezoelectric pump 21, periodic changes
in the volume of and pressure in the pump chamber 25 are repeatedly
produced by bending and vibration of the piezoelectric element 22
and the diaphragm 28, and an inertial force begins to act on the
flow of gas. This allows a fluid (gas) in the flow passage 24 to be
constantly discharged from the discharge port 26. In the
piezoelectric pump 21, the diaphragm 28 faces the discharge port 26
with the flow passage 24 and the pump chamber 25 interposed
therebetween. This improves fluid efficiency of the piezoelectric
pump 21, and allows even a high-viscosity fluid, such as nasal
mucus, to be easily suctioned by the aspirator 10.
FIG. 4 is a block diagram of the circuit unit 31. The circuit unit
31 feeds back a current flowing through the piezoelectric element
22 to automatically regulate a drive voltage (output voltage)
applied to the piezoelectric element 22. The circuit unit 31
includes a current detector 32, a regulator 33, a voltage
controller 34, and a drive circuit 35. The current detector 32
measures a current flowing through the piezoelectric element 22.
The regulator 33 determines the state of the front end of the
nozzle 11 (hereinafter referred to as a nozzle end) on the basis of
the measurement result of the current detector 32. The voltage
controller 34 outputs a voltage having a predetermined pattern on
the basis of the determination made by the regulator 33. The
voltage controller 34 is supplied with power from a power source
36. The drive circuit 35 generates a drive voltage by boosting the
voltage output by the voltage controller 34, and applies the drive
voltage to the piezoelectric element 22. Note that the circuit unit
31 is obtained by mounting electronic components on a circuit
board. The current detector 32 and the regulator 33 correspond to a
detecting unit of the present disclosure. The regulator 33 and the
voltage controller 34 correspond to a control unit of the present
disclosure.
The nozzle end communicates with the suction port 27 of the
piezoelectric pump 21 (see FIG. 2). This means that the current
detector 32 and the regulator 33 detect the closed state of the
suction port 27. Also, the regulator 33 and the voltage controller
34 regulate the output voltage for the piezoelectric element 22 in
accordance with the detected closed state of the suction port 27.
The indicator displays the detected closed state of the suction
port 27.
FIG. 5 is a graph showing the amplitude of the current flowing
through the piezoelectric element 22 with respect to the amplitude
of the drive voltage applied to the piezoelectric element 22. For
an amplitude V of each drive voltage, a current amplitude
I.sub.c(V) obtained when the nozzle end is closed differs from a
current amplitude I.sub.o(V) obtained when the nozzle end is
open.
Thus, if a current amplitude I measured by the current detector 32
is close to the current amplitude I.sub.c(V), that is, if
I-I.sub.c(V)|<.delta. holds for a predetermined value
.delta.>0, the regulator 33 determines that the nozzle end is
closed. If the current amplitude I is close to the current
amplitude I.sub.c(V), that is, if |I-I.sub.o(V)|<.delta. holds,
the regulator 33 determines that the nozzle end is open. The
current amplitude I.sub.c(V) and the current amplitude I.sub.o(V)
may be calculated as needed, or may be stored in the form of a
table. Although the amplitude V of the drive voltage is held by the
regulator 33, it may be acquired by measurement.
As illustrated in FIG. 5, for the amplitude V of each drive
voltage, the current amplitude I.sub.c(V) is greater than the
current amplitude I.sub.o(V). Therefore, the state of the nozzle
end may be determined by comparing the current amplitude I with a
threshold I.sub.t(V) which is appropriately set in the range of
I.sub.o(V)<I.sub.t(V)<I.sub.c(V).
The magnitude of the impedance of the piezoelectric element 22 is
the amplitude ratio between the current flowing through the
piezoelectric element 22 and the drive voltage. This means that the
determination made by the regulator 33 involves using the magnitude
of the impedance of the piezoelectric element 22 at a drive
frequency (i.e., the frequency of the drive voltage). Also, the
suction pressure is high when the current amplitude I is close to
the current amplitude I.sub.c(V) and low when the current amplitude
I is close to the current amplitude I.sub.o(V). This means that the
regulator 33 determines the state of the nozzle end by indirectly
detecting the suction pressure. Here, the suction pressure is a
pressure difference between the side of the suction port 27 and the
side of the discharge port 26 in the piezoelectric pump 21 (see
FIG. 2). Also, the flow rate is low when the current amplitude I is
close to the current amplitude I.sub.c(V) and high when the current
amplitude I is close to the current amplitude I.sub.o(V). This
means that the regulator 33 determines the state of the nozzle end
by indirectly detecting the flow rate. Here, the flow rate is the
amount of air flowing from the suction port 27 to the discharge
port 26 of the piezoelectric pump 21.
FIG. 6 is a flowchart illustrating an operation of the circuit unit
31. The drive circuit 35 applies an initial voltage as a drive
voltage to the piezoelectric element 22 (S11). After the elapse of
a given time (e.g., about 1 second) (S12), the current detector 32
measures a current flowing through the piezoelectric element 22
(S13). If the current amplitude I of the measured current is close
to the current amplitude I.sub.c(V), the regulator 33 determines
that the nozzle end is closed, that is, the suctioning of nasal
mucus has failed (Yes in S14). In this case, for removal of the
nasal mucus, the drive circuit 35 applies a drive voltage having an
amplitude greater by a predetermined value than the original
amplitude to the piezoelectric element 22 (S15). If increasing the
amplitude of the drive voltage causes it to exceed a limit value,
the amplitude of the drive voltage is kept the same as the original
amplitude.
If the current amplitude I is close to the current amplitude
I.sub.o(V), the regulator 33 determines that the nozzle end is open
(No in S14, Yes in S16). That is, the regulator 33 determines that
suctioning of the nasal mucus has succeeded, or that the nozzle end
is not in contact with the nasal mucus in the nasal cavity. In this
case, step S11 is performed again. If the current amplitude I is
far from both the current amplitude I.sub.c(V) and the current
amplitude I.sub.o(V), the regulator 33 determines that the
aspirator 10 has malfunctioned (No in S14, No in S16). In this
case, the suctioning operation is terminated and the indicator
displays an error message. If the current amplitude I is close to
the current amplitude I.sub.o(V), the regulator 33 may terminate
the suctioning operation on the basis of the determination that the
suctioning of the nasal mucus has succeeded.
FIG. 7A is a conceptual diagram illustrating how the amplitude of
the drive voltage changes with time in suctioning of low-viscosity
nasal mucus. FIG. 7B is a conceptual diagram illustrating how the
amplitude of the drive voltage changes with time in suctioning of
medium-viscosity nasal mucus. FIG. 7C is a conceptual diagram
illustrating how the amplitude of the drive voltage changes with
time in suctioning of high-viscosity nasal mucus. Time t.sub.c
represents the time when suctioning of nasal mucus has been
completed. Note that the time difference between voltage adjustment
and current measurement is not taken into account in FIGS.
7A-7C.
FIG. 7A shows that suctioning of low-viscosity nasal mucus is
completed when the amplitude of the drive voltage is at an initial
voltage amplitude V.sub.ini; that is, the amplitude of the drive
voltage is kept unchanged. FIG. 7B shows that in suctioning of
medium-viscosity nasal mucus, the amplitude of the drive voltage
increases with time from the initial voltage amplitude V.sub.ini,
and returns to the initial voltage amplitude V.sub.ini at the
completion of the suctioning. FIG. 7C shows that in suctioning of
high-viscosity nasal mucus, as compared to the case of suctioning
the medium-viscosity nasal mucus, it takes more time to complete
the suctioning and the amplitude of the drive voltage at the
completion of the suctioning is larger. The aspirator 10 thus
automatically regulates the drive voltage in accordance with the
viscosity of the nasal mucus.
FIG. 8A is a conceptual diagram illustrating how the amplitude of
drive voltage, the suction pressure, and the flow rate change with
time in an aspirator having a conventional configuration. FIG. 8B
is a conceptual diagram illustrating how the amplitude of drive
voltage, the suction pressure, and the flow rate change with time
in the aspirator 10. Note that the amplitude of drive voltage, the
suction pressure, the flow rate, and time are appropriately
normalized in FIGS. 8A and 8B.
In the aspirator having the conventional configuration, as
illustrated in FIG. 8A, the amplitude of the drive voltage is
always constant. In the range of time from 0 to 4 and from 9 to 12,
the suction pressure is 0 because the nozzle end is open, and the
flow rate is excessively high because the amplitude of the drive
voltage is regulated to be suitable for the nozzle end in the
closed state. In the range of time from 4 to 9, where the nozzle
end is closed, the suction pressure is higher than that when the
nozzle end is open, and the flow rate is lower than that when the
nozzle end is open.
In the aspirator 10, the amplitude of the drive voltage is
automatically regulated as illustrated in FIG. 8B. In the range of
time from 0 to 4 and from 9 to 12, the suction pressure is 0
because the nozzle end is open. Also, the amplitude of the drive
voltage is kept small, and the flow rate is kept at a moderate
level. In the range of time from 4 to 9, the nozzle end is closed.
Accordingly, the amplitude of the drive voltage is greater than
that when the nozzle end is open, and the suction pressure is
higher than that when the nozzle end is open. Because of the large
amplitude of the drive voltage, the flow rate is not significantly
reduced from that when the nozzle end is open.
Every time the aspirator 10 determines that the nozzle end is
closed, the aspirator 10 increases the amplitude of the drive
voltage. Also, when the aspirator 10 determines that the nozzle end
is open, the aspirator 10 reduces the amplitude of the drive
voltage. Thus, when it is difficult to suction the nasal mucus, the
amplitude of the drive voltage is increased and the nasal mucus is
suctioned by high suction pressure. When it is easy to suction the
nasal mucus, the amplitude of the drive voltage is kept at a medium
level, and the nasal mucus is suctioned by low suction pressure.
When suctioning of the nasal mucus is completed or there is no
nasal mucus, the amplitude of the drive voltage is reduced. Thus,
with the aspirator 10, the nasal mucus can be suctioned by
appropriate suction pressure in accordance with the closed state of
the nozzle end. Additionally, since the aspirator 10 can operate at
a minimum drive voltage, power consumption during operation can be
reduced. Also, when suctioning of the nasal mucus is completed or
there is no nasal mucus, the amplitude of the drive voltage is
reduced and it is unlikely that a large amount of air is suctioned
out of the nasal cavity. A negative impact on the human body can
thus be reduced.
Second Embodiment
An aspirator according to a second embodiment of the present
disclosure will be described. FIG. 9 is a block diagram of a
circuit unit 41 according to the second embodiment. The circuit
unit 41 includes a current detector 42, a voltage detector 43, a
phase comparator 44, a microcontroller (MCU) 45, and a resistor 46.
The current detector 42 measures a current flowing through the
piezoelectric element 22 by measuring a voltage across both ends of
the resistor 46 whose resistance value is known. The resistor 46 is
inserted in a voltage line that connects the piezoelectric element
22 to the drive circuit 35. The voltage detector 43 measures a
drive voltage applied to the piezoelectric element 22. The phase
comparator 44 outputs a phase difference .theta. between the
current measured by the current detector 42 and the voltage
measured by the voltage detector 43. The microcontroller 45 outputs
a voltage having a predetermined pattern to the drive circuit 35 on
the basis of the phase difference .theta. output by the phase
comparator 44.
A circuit-type digital comparator, such as a phase frequency
comparator used in a phase-locked loop (PLL) or the like, is used
as the phase comparator 44. The microcontroller 45 used is one
having an I/O terminal and a PWM output terminal. The I/O terminal
is connected to the phase comparator 44, and the PWM output
terminal is connected to the drive circuit 35.
A phase difference .theta..sub.c between the current flowing
through the piezoelectric element 22 and the drive voltage when the
nozzle end is closed differs from a phase difference .theta..sub.o
between the current flowing through the piezoelectric element 22
and the drive voltage when the nozzle end is open. Therefore, when
the phase difference .theta. is close to the phase difference
.theta..sub.c, the microcontroller 45 determines that the nozzle
end is closed, whereas when the phase difference .theta. is close
to the phase difference .theta..sub.o, the microcontroller 45
determines that the nozzle end is open. The phase of the impedance
of the piezoelectric element 22 is a phase difference between the
current flowing through the piezoelectric element 22 and the drive
voltage. This means that the determination made by the
microcontroller 45 involves using the phase of the impedance of the
piezoelectric element 22 at a drive frequency.
FIG. 10 is a flowchart illustrating an operation of the circuit
unit 41. The phase comparator 44 outputs a phase difference .theta.
after step S12 (S23). The microcontroller 45 compares the phase
difference .theta. with the phase difference .theta..sub.c, and
also compares the phase difference .theta. with the phase
difference .theta..sub.o if necessary, thereby determining the
state of the nozzle end (S24, S26).
In the second embodiment, the state of the nozzle end can be
detected by measuring the phase difference .theta. between the
current flowing through the piezoelectric element 22 and the drive
voltage. Since the measurement of the phase difference .theta. is
less affected by changes in temperature, it is possible to
accurately regulate the suction pressure.
Third Embodiment
An aspirator according to a third embodiment of the present
disclosure will be described. FIG. 11 is a block diagram of a
circuit unit 51 according to the third embodiment. The circuit unit
51 includes a resonant frequency computing unit 57. The resonant
frequency computing unit 57 calculates a resonant frequency f of
the piezoelectric element 22 on the basis of the current measured
by the current detector 32. The regulator 33 determines the state
of the nozzle end on the basis of the resonant frequency f
calculated by the resonant frequency computing unit 57.
The resonant frequency of the piezoelectric element 22 is a
frequency at which the magnitude of the impedance of the
piezoelectric element 22 is minimized, that is, a frequency at
which the amplitude of the current flowing through the
piezoelectric element 22 is maximized. The resonant frequency of
the piezoelectric element 22 can be calculated by varying the drive
frequency within a predetermined range, measuring the current
flowing through the piezoelectric element 22 at each frequency, and
selecting a frequency at which the amplitude of the measured
current is maximized.
A resonant frequency f.sub.c of the piezoelectric element 22 when
the nozzle end is closed differs from a resonant frequency f.sub.o
of the piezoelectric element 22 when the nozzle end is open.
Therefore, when the resonant frequency f is close to the resonant
frequency f.sub.c, the regulator 33 determines that the nozzle end
is closed, whereas when the resonant frequency f is close to the
resonant frequency f.sub.o, the regulator 33 determines that the
nozzle end is open.
FIG. 12 is a flowchart illustrating an operation of the circuit
unit 51. The resonant frequency computing unit 57 calculates the
resonant frequency f after step S12 (S33). The regulator 33
compares the resonant frequency f with the resonant frequency
f.sub.c, and also compares the resonant frequency f with the
resonant frequency f.sub.o if necessary, thereby determining the
state of the nozzle end (S34, S36). The drive circuit 35 applies a
drive voltage appropriate for the state of the nozzle end to the
piezoelectric element 22 (S11, S15). The drive frequency is
adjusted to the resonant frequency f.
In the third embodiment, the state of the nozzle end can be
detected by calculating the resonant frequency f of the
piezoelectric element 22. Also, by adjusting the drive frequency to
the resonant frequency f, it is possible to increase the vibration
of the piezoelectric element 22 and achieve high suction pressure
without necessarily varying the amplitude of the drive voltage.
Although the aspirator of each of the embodiments described above
is a nasal mucus aspirator, the aspirator of the present disclosure
is not limited to the nasal mucus aspirator, and may be one that
suctions body fluid, such as saliva or phlegm.
Fourth Embodiment
An aspirator for a negative pressure wound therapy according to a
fourth embodiment of the present disclosure will be described. FIG.
13 is a schematic cross-sectional view for explaining a negative
pressure wound therapy according to the fourth embodiment. The
negative pressure wound therapy involves covering a wounded portion
W of the patient with a dressing 67, such as a gauze dressing. The
wounded portion W covered with the dressing 67 is hermetically
sealed with a film 66. A first end of a tube 64A passes through an
opening of the film 66 and is connected to the dressing 67. A
second end of the tube 64A is connected to a storage unit 65. The
storage unit 65 is connected to an aspirator 60 by a tube 64B
extending therebetween. A flow passage that connects the dressing
67 to the aspirator 60 is thus created.
The aspirator 60 has, for example, the same configuration as the
piezoelectric drive unit of the first embodiment. The piezoelectric
drive unit includes a piezoelectric pump and a circuit unit for
driving the piezoelectric pump, as described above. In the negative
pressure wound therapy, the aspirator 60 suctions air in the
dressing 67 to lower the pressure in the dressing 67. Also, the
negative pressure wound therapy involves suctioning exudate
accumulated in the dressing 67 together with air, separating the
exudate from the air, and storing the exudate in the storage unit
65.
FIG. 14 is a flowchart illustrating an operation of the aspirator
60. The aspirator 60 operates in the following manner. The
aspirator 60 sets the drive voltage of the piezoelectric pump to a
standard voltage, and drives the piezoelectric pump to suction air
in the dressing 67 (S41). When the pressure in the dressing 67 is
lowered to a lower limit by this suctioning, a suction portion
(suction port) of the piezoelectric pump approaches a closed state.
After the elapse of a given time (S12), the aspirator 60 detects
the state of the suction portion of the piezoelectric pump (S43).
For example, as in the first embodiment described above, the state
of the suction portion of the piezoelectric pump is detected by
measuring current flowing through a piezoelectric element of the
piezoelectric pump. If the suction portion of the piezoelectric
pump is detected to be in the closed state (Yes in S44), the
aspirator 60 lowers the drive voltage of the piezoelectric pump to
a minimum voltage at which detection of the closed state is
generally possible (S45). Then, the aspirator 60 performs step S12
again.
Lowering the drive voltage of the piezoelectric pump lowers the
suction force of the piezoelectric pump. As time elapses, air
begins to flow into the dressing 67 through a narrow gap between
the film 66 and the skin of the patient, or between the film 66 and
the tube 64A. When this causes the pressure in the dressing 67 to
reach an upper limit, the suction portion of the piezoelectric pump
approaches the open state. If suctioning of air in the dressing 67
is not yet sufficient enough, the suction portion of the
piezoelectric pump remains close to the open state. If the suction
portion of the piezoelectric pump is detected to be in the open
state (No in S44, Yes in S46), the aspirator 60 drives the
piezoelectric pump at the standard voltage to suction air in the
dressing 67 (S41). If the suction portion of the piezoelectric pump
is detected to be neither in the closed state nor in the open state
(No in S44, No in S46), the aspirator 60 determines that a
malfunction has occurred, and terminates the suctioning
operation.
In the fourth embodiment, when pressure in the dressing 67 reaches
a lower limit, the drive voltage of the piezoelectric pump is
lowered to a minimum voltage. This makes it possible not only to
prevent excessive suction, but also to reduce power consumption.
Also, when pressure in the dressing 67 reaches an upper limit,
suctioning of air in the dressing 67 is resumed. It is thus
possible to keep pressure in the dressing 67 at a low level.
Fifth Embodiment
An anti-bedsore bed using a pressurizer according to a fifth
embodiment of the present disclosure will be described. FIG. 15A is
an external perspective view of an anti-bedsore bed 70 according to
the fifth embodiment. FIG. 15B is an exploded perspective view of
the anti-bedsore bed 70 according to the fifth embodiment. A
rectangular upper surface of a base 74 is provided with air cells
73A and 73B thereon. The air cells 73A and 73B are arranged side by
side in the direction of the short side of the upper surface of the
base 74, and are longer in the longitudinal direction of the upper
surface of the base 74. A mat 71 formed by joining the side faces
of a plurality of columnar air cells 72 is placed over the upper
surface of the base 74 having the air cells 73A and 73B
thereon.
The air cells 72, 73A, and 73B are connected by corresponding tubes
(not shown) to a pressurizer (not shown). The pressurizer includes
piezoelectric pumps corresponding to the respective air cells,
drive circuit units for driving the respective piezoelectric pumps,
and a control circuit unit configured to control the timing of the
operation of each of the drive circuit units. The piezoelectric
pumps are each configured, for example, in the same manner as in
the first embodiment. The drive circuit units are each configured,
for example, in the same manner as the circuit unit of the first
embodiment. The piezoelectric pumps are each positioned with its
discharge portion (discharge port) facing the corresponding tube
and its suction portion facing the outside air.
The tube connected to the air cells 72 is provided with a valve.
This allows air to be introduced into or discharged from the air
cells 72 as necessary. The tubes connected to the air cells 73A and
73B are not provided with any valves. Thus, when the piezoelectric
pumps are driven, air is supplied to the air cells 73A and 73B,
which are thus pressurized. When the piezoelectric pumps are
stopped, air is discharged from the air cells 73A and 73B, and the
pressure in the air cells 73A and 73B is reduced.
FIG. 16A is a side view of the anti-bedsore bed 70. FIG. 16B is a
side view of the anti-bedsore bed 70 in which the air cell 73A is
inflated. In the anti-bedsore bed 70, one of the air cells 73A and
73B is inflated by the pressurizer to raise one side of the body of
a user P. This allows the user P to turn over. The air cells 72 may
be used, along with the air cells 73A and 73B, to allow the user P
to turn over.
FIG. 17 is a flowchart illustrating an operation of the drive
circuit unit corresponding to the air cell 73A. The drive circuit
unit corresponding to the air cell 73B operates in the same manner
as the drive circuit unit corresponding to the air cell 73A. The
drive circuit unit operates in the following manner. After driving
the piezoelectric pump corresponding to the air cell 73A at an
initial voltage (S11) and a given time (e.g., about 0.1 seconds)
elapses (S12), the drive circuit unit measures a current flowing
through the piezoelectric pump corresponding to the air cell 73A
(S13). If the user has not yet turned over, the air cell 73A is
held under pressure by the weight of the user. Therefore, the
current flowing through the piezoelectric pump corresponding to the
air cell 73A is close to the current amplitude I.sub.c(V) obtained
when the discharge portion of the piezoelectric pump is in the
closed state. Accordingly, if the amplitude of the measured current
is close to the current amplitude I.sub.c(V), the drive circuit
unit determines that the user has not turned over (Yes in S14).
Then, the drive circuit unit raises the drive voltage of the
piezoelectric pump corresponding to the air cell 73A to continue to
apply pressure to the air cell 73A (S15).
When the user turns over, the body of the user is separated from
the air cell 73A. This brings pressure in the air cell 73A close to
the atmospheric pressure. Therefore, the current flowing through
the piezoelectric pump corresponding to the air cell 73A is close
to the current amplitude I.sub.o(V) obtained when the discharge
portion of the piezoelectric pump is open. Accordingly, if the
amplitude of the measured current is close to the current amplitude
I.sub.o(V) (No in S14, Yes in S16), the drive circuit unit
determines that the user has turned over. Then, the drive circuit
unit stops the piezoelectric pump corresponding to the air cell 73A
to stop the application of pressure to the air cell 73A until the
next timing of turning over (S57). At the next timing of turning
over, the drive circuit unit drives the piezoelectric pump
corresponding to the air cell 73A at the initial voltage again
(S11). Note that the timing of operation of each of the drive
circuit units corresponding to the air cells 73A and 73B is
controlled by the control circuit unit such that the air cells 73A
and 73B are alternately pressurized.
In the fifth embodiment, the amplitude of the drive voltage of the
piezoelectric pump is increased when the user does not turn over,
whereas the piezoelectric pump is stopped when the user turns over.
Thus, by simply driving the piezoelectric pump for a minimum period
of time at a minimum output, it is possible to allow the user to
turn over and prevent the user's bedsore. In step S15 of the fifth
embodiment, the drive circuit unit may keep the drive voltage of
the piezoelectric pump unchanged, instead of raising it. Even in
this case, an effect close to that in the case of raising the drive
voltage of the piezoelectric pump can be achieved.
REFERENCE SIGNS LIST
10, 60: aspirator
11: nozzle
12: separator
13: piezoelectric drive unit
14, 24: flow passage
15, 65: storage unit
21: piezoelectric pump (pump)
22: piezoelectric element
23: structure
25: pump chamber
26: discharge port (discharge portion)
27: suction port (suction portion)
28: diaphragm
31, 41, 51: circuit unit
32, 42: current detector (detecting unit)
33: regulator (detecting unit, control unit)
34: voltage controller (control unit)
35: drive circuit
36: power source
43: voltage detector
44: phase comparator
45: microcontroller
46: resistor
57: resonant frequency computing unit
64A, 64B: tube
66: film
67: dressing
70: anti-bedsore bed
71: mat
72, 73A, 73B: air cell
74: base
P: user
W: wounded portion
* * * * *